As previously mentioned, you can eliminate all printing costs for your event by uploading your content and material onto your app. Not only is it more accessible, guests are also far less likely to forget to bring their phone than their event program sheet.
Last minute changes? Even the most experienced event organisers will encounter this during an event. Pulling off a successful event requires countless hours of planning and detailed consideration but a small change is enough to ruin all the efforts. Personally, I have seen many speakers going up to the event organisers to update their slides